The U.S. Supreme Court is scheduled to hear arguments Wednesday in a dispute over the level of education that public schools must provide to millions of children with disabilities, a case that advocates describe as the most significant special-education issue to reach the high court in three decades.

The question is whether public schools owe disabled children “some” educational benefit — which courts have determined to mean just-above-trivial progress — or whether students legally deserve something more: a substantial, “meaningful” benefit.

Lower courts are divided on the question, meaning that disabled children in some states can expect more from their schools than children in other states. Now the Supreme Court will have an opportunity to decide whether a uniform standard should apply nationally.

To advocates for children with disabilities, this should not be a difficult decision. Although the Supreme Court upheld the lower standard in 1982, Congress has since amended the federal Individuals With Disabilities Education Act (IDEA). The law — which outlines what states must do in return for receiving federal special-education funds — is meant not just to open the schoolhouse door to disabled children, they argue, but also to make sure that those children get an education that gives them a shot at equal opportunity, independent life and full participation in society.

That means schools must be required to provide students with a real, meaningful education, they argue. “I can’t even believe that this is really a question for the court to wrestle with,” said Gary Mayerson, a civil rights lawyer and board member of Autism Speaks, an advocacy organization.

But lawyers for Colorado’s Douglas County School District — the defendant in the case before the court — argue that the “meaningful” benefit standard is ambiguous, not grounded in law and not practical. Judges aren’t proficient in education policy and can’t be expected to decide whether schools are meeting such a vague and variable standard, they argue.

The case to be heard Wednesday is Endrew F. v. Douglas County School District, brought by the family of a boy diagnosed with autism and attention-deficit/hyperactivity disorder. His conditions complicated his efforts to communicate and socialize, and that left him struggling with phobias and compulsive behaviors.

Endrew F., who goes by Drew, started attending schools in Douglas County — south of Denver — in preschool and began showing an increase in behavioral problems in the second grade, according to court records. He was yelling, crying and dropping to the floor. By fourth grade, the problems had become more frequent and severe; he was kicking walls, banging his head and bolting from the classroom. He went to the bathroom on the floor of a “calming room,” and he was able to escape from the school building and run into the street.

His parents said their son made almost no academic or social progress over that period, and they didn’t see a commitment from the district to find a solution. The goals in his Individualized Education Program (IEP) — a legally binding blueprint that laid out the services he would receive and the progress he was expected to make — hardly changed from year to year, according to court records, and there was little written evidence that he was making gains.

Drew’s parents withdrew him from public school at the end of fourth grade, in 2010, and placed him in a private school that specialized in educating children with autism. He made progress immediately, they said, achieving IEP goals in months that he had been working on for years.

It was a relief.

Drew, now 17, continues to attend the private school, his parents said, where he is learning vocational skills and preparing for life after high school.

Under federal law, Drew’s parents were entitled to seek reimbursement for the private school tuition, which approached $70,000 per year. But they had to prove that their son had been denied the “free appropriate public education” to which he had a right under federal special-education law. And to do so, they had to prove that he hadn’t been making adequate progress.

Jack Robinson, their attorney, has been working in special-education law for 20 years, and he thought that if any child could win a case like this, it was Drew. There was almost no documented progress in Drew’s educational records, he said in an interview.

But the Douglas County School District disagreed, arguing that while Drew was not learning as quickly as his parents would have liked, he was making some progress — enough to satisfy the law.

The family lost its case before an administrative law judge in 2012. They lost again in a suit in U.S. District Court and a third time at the U.S. Court of Appeals for the 10th Circuit.

“This is without question a close case,” Judge Timothy Tym­kovich wrote in his opinion for the 10th Circuit. It is clear, he continued, that Drew is thriving at the private school. “But it is not the District’s burden to pay for his placement there when Drew was making some progress under its tutelage. That is all that is required.”

The court’s endorsement of that low bar was a blow to Drew’s parents. “What is the point of the law, if it doesn’t help the child?” said his mother, Jennifer.

In their briefs to the Supreme Court, Drew and his family argued that schools should be obligated to provide children with disabilities with “substantially equal opportunities to achieve academic success, attain self-sufficiency and contribute to society.” They won the support of the Obama administration, whose Justice Department submitted an amicus brief calling on the high court to find a requirement that children have an opportunity to make “significant educational progress.”

More than 100 members of Congress also support Drew and his parents, arguing in an amicus brief that the just-above-trivial standard is “vanishingly low” and runs contrary to Congress’s intent in IDEA.

The Douglas County School District disagrees, arguing that the Supreme Court’s decision in a 1982 case, Board of Education v. Rowley, should stand. In that case, the court rejected the argument that schools owed disabled children an opportunity to maximize their potential. The justices ruled that Congress intended to ensure “some educational benefit” for children with disabilities, the standard that has been explicitly adopted by five Circuit Courts of Appeals.

“This Court answered the question presented 34 years ago,” lawyers for the school district wrote in a brief last month. “That decision was correct.”

(In Rowley, the justice also said that Congress intended to make “access meaningful” for students with disabilities, giving rise to the “meaningful” educational benefit standard that has been adopted by two circuits.)

The school district’s lawyers have argued in briefs that Drew and his family are seeking a “sweeping new standard” that has no basis in IDEA and that courts would be unable to enforce given the complications of determining what that standard means in practice for children with different disabilities and circumstances.

The district’s supporters include the National School Boards Association and AASA, an association of district superintendents, which both argued that raising expectations of schools could encourage more litigation.

William E. Trachman, the district’s legal counsel, declined through a spokeswoman to discuss the facts of the case given the pending litigation.

“The District complies with every facet of federal law in making sure that students with special needs are not only provided services, but that educational experts and the student’s parents are maximally involved in the process, and that every Individualized Education Plan is personalized, holistic and ambitious,” Trachman said in a statement.